 body {
     background-color: #f7e6e6;
     opacity: 0.8;
     background-image: radial-gradient(#f74545 1.05px, transparent 1.05px), radial-gradient(#f74545 1.05px, #f7e6e6 1.05px);
     background-size: 42px 42px;
     background-position: 0 0, 21px 21px;
 }
 
 h2 {
     width: 100%;
     height: 100%;
     margin-top: 50px;
     letter-spacing: 2px;
     font-size: 30px;
     text-align: center;
     font-style: italic;
     opacity: 0.9;
     color: #f4ab3c;
     text-shadow: 2px 3px 3px #000;
 }
 
 #canvas {
     display: block;
     margin: 30px auto;
     border-radius: 10px;
     box-shadow: 5px 5px 10px 5px rgb(0 0 0 / 30%);
 }
 
 .filebutton {
     position: relative;
     left: 50%;
     transform: translateX(-50%);
     /* 跟着内部文本变化 */
     display: inline-block;
     overflow: hidden;
 }
 
 .filebutton input {
     position: absolute;
     top: 0;
     opacity: 0;
     /* 通过字体把input宽弄大，但是由于父亲跟着div宽度，也使得input超出隐藏 */
     font-size: 50px;
 }
 
 .filebutton div {
     font-size: 15px;
     letter-spacing: 2px;
     background-color: #f39c12;
     color: white;
     border-radius: 15px;
     padding: 8px 25px;
 }
 
 .btn {
     display: block;
     margin: 5px auto;
     padding: 9px 25px;
     font-size: 15px;
     border-radius: 15px;
     color: #fff;
     letter-spacing: 2px;
     background-color: #f39c12;
 }
 
 .title {
     margin-top: 50px;
     margin-right: 80px;
     text-align: right;
 }
 
 .title span {
     display: block;
     font-size: 20px;
     color: #f4ab3c;
     font-style: italic;
     text-shadow: 1px 1px 3px #000;
 }